ORLANDO – Temozolomide, an alkylating agent approved for glioblastoma, improved long-term survival in about half of patients who took it for aggressive pituitary tumors, a retrospective study has determined.

The study, conducted by members of the French Society of Endocrinology, comprised 43 patients. Of the 51% who responded to the treatment, the median overall survival time was 44 months, compared to just 16 months for patients who didn’t respond, Gérald Raverot, MD, said at the annual meeting of the Endocrine Society.

The study, which has been accepted for publication in the European Journal of Endocrinology, is a small bright spot for patients who have very few options, said Dr. Raverot of the University Hospital Center of Lyon, France. But although the drug improved survival, it is not a cure.

“Despite the very good response we saw in some patients, we also saw a high risk of recurrence, with a median of about 30 months,” for relapse, he noted. “And a second course of temozolomide always failed.”

When used for aggressive pituitary tumors, temozolomide is usually given in a conventional scheme of up to 12 cycles. It’s typically reserved for tumors that have responded poorly to other treatment regimens, Dr. Raverot said.

The drug has not been widely studied in patients with aggressive pituitary tumors, although there have been a number of case reports suggesting that can be beneficial. Data on about 90 patients have been published. The largest series to date appeared in 2015 and comprised 24 patients. It found about a 50% response rate to the drug. Two patients had a complete regression and seven patients had a partial regression of tumor mass. Tumor mass shrunk to less than 30% in three patients, less than 50% in three, and less than 75% in one.

Because of both the promise temozolomide shows in these very tough cases, and the paucity of descriptive and clinical data, Dr. Raverot and his colleagues conducted a multi-center study that spanned 21 facilities in France and comprised 43 patients who were treated from 2006-2016. The intent was to evaluate efficacy at the end of treatment, or at last follow-up in the case of those who were still being treated. Tumor response was defined as a decrease of more than 30% in the largest tumor diameter; hormonal response was more than a 50% decrease in baseline hormone levels. The endpoint was overall survival and relapse-free survival.

Of the 43 patients, 29 were men. The group’s mean age at diagnosis was 43 years, and the mean age at temozolomide treatment, 53 years. Fourteen of the tumors were carcinomas and 12 were silent or initially silent.

About half of the tumors (23) were adrenocorticotropic hormone-producing. Other tumor types were prolactin-secreting (13) and growth hormone-secreting (3); an additional three tumors secreted both prolactin and growth hormone.

Most patients (36) underwent a typical temozolomide protocol. This consisted of at least one 5-day cycle of 150 mg/m²/day every 28 days, followed by 250 mg/m²/day thereafter. The median number of cycles was 6.5, but this ranged from 1-24 cycles.

Six patients were treated according to the Stupp protocol for temozolomide in glioblastoma. This consists of daily temozolomide 75 mg/m² with concomitant radiotherapy for 6 weeks, followed by a standard temozolomide protocol. Four patients underwent 6 cycles; one patient 12 cycles, and one patient, 17 cycles.

An additional four patients had concomitant radiotherapy within 4 months of their temozolomide treatment.

The overall response rate was 51% (22 patients). Dr. Raverot attempted to identify clinical characteristics predictive of response. There was no association with gender, age at diagnosis or age at temozolomide treatment, tumor type, whether or not the tumor was a carcinoma, or what type of hormone it secreted. Nor was there a response associated with hypermethylation of the O6-methylguanine-DNA-methyltransferase (MGMT) gene.

Dr. Raverot found only one positive association with response. Tumors that were silent or initially silent (12) were much less likely to respond than secreting tumors. Of the 21 nonresponsive tumors, 10 were silent (45%). Of the 22 responsive tumors, only 2 were silent (9%).

Dr. Raverot also analyzed response by protocol and found intriguing results. Of the 10 patients who had concomitant radiotherapy, seven responded and three did not. Patients who underwent the Stupp protocol also tended to do better, he said. “Of the six who had this, five responded, so this is interesting.”

However, he cautioned, both of these positive associations are based on such small numbers that it’s impossible to draw firm conclusions.

Dr. Raverot had survival data on 38 patients with a median follow-up of 16 months after the end of treatment. Of these, 20 were responders and 18 were non-responders. Death had occurred in 13 of the nonresponders and five responders.

Of the 20 responders, 10 were still controlled at the time of last follow-up, and 10 had relapsed at a median of 5 months after treatment cessation. Five of these patients had a second course of temozolomide, but none of them responded to it, Dr. Raverot said. Three of these patients have died and two are still living.

“We looked at other salvage treatments for them, but none of these therapies could control the disease. Unfortunately, we just don’t have good treatment options for these patients. And even among those with good treatment response, there is a risk of early recurrence, with a median time of 30 months to relapse. The second course of temozolomide always fails. So we have now some questions about who we should maintain on treatment. We don’t have this answered yet, and we need to.”

Dr. Raverot had no financial disclosures.

msullivan@frontlinemedcom.com

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Temozolomide may help half of patients with aggressive pituitary tumors